Radio receiving apparatus



March 23 1926.

RADIO RECEIVING APPARATUS Filed Feb. 4, 1925 2 Sheets-Sheet 1 p I 3Z8 Ia! Fig.2.

awwwb'oz March 23 1926. 1,577,613

F. w. DUNMORE RADIO RECEIVING APPARATUS Filed Feb. 4, 1925 2 Sheds-Sheet 2 Patented 23, 1 926 uNir-l-los fr rss PATENT orifice.

more w. DUNMORE, or wasnme'rou, nrsriucr or COLUMBIA."

I RADIO RECEIVING APPARATUS.

' Application filed February 4, 1925. Serial 1T0. 6,898.

To all uilzom it may concern:

Be it known that I, FRANCIS W. DUN- Moim, citizen of the United States, residing at Washington, District of Columbia, have invented certain new andv useful Improvements in Radio Receiving Apparatus, of

which the following is a specification.

My present invention relates broadly to radio receiving apparatus and more particu- 3 larly to' means for simplifying the operation of such apparatus. The object of the invention is to provide means whereby by means of one manual control the electrical constants of two or more different circuits may be maintained in a definite relation with respect to each other as the constants of l each circuit are varied. r

One of the best methods of obtaining selectivity in radioreceiving apparatus is either by means of the Armstrong superheterodyne principle of Letters Patent, 1,342,885 dated June 8, 1920 whereja beat frequency is made use 'of, or by tuned multi-stage radio frequency amplification, each stage being tuned to be resonant to thesame frequency either by means of a tuning condenser or variable inductance in each stage. In the former case two variable controls, loop or antenna tuning and heterodyne oscillator tuning are required. In the latter case, a variable tuning controlfor each tuned. stage is necessary. Naturally, this multiplicity of controls complicates the operation of the apparatus It is impossible to accomplish this end by means of rotating two or more condensers or variometers' on the same shaft adjusting the frequency of the heterodyne oscillator to that necessary to give the desired intermediate frequency. In attaining my object of reducing these two controls to one I mount the variable elements, either capacity or inductance, so as to be rotatable on the same shaft, or gear'connected, said shaft or gears being rotated by means of one control. Rotating with saidshaft or gears is a cam which in turn operates a vernier compensating condenser or inductance electrically connected to either'of the two circuits requiring adjustment. The cam is so shaped that the correct frequency relationsare maintained between the two circuits over acontinuous range of frequencies.

A further object of my invention is to provide means of tuning bynleans of one control several independent circuits consisting of inductance and capacity so that each circuit will be continuously resonant to the same frequency over a continuous range of frequencies. By way of example; take the present type of multituned radio frequency amplifier receiving set, there beingthree tuned stages, this means three independent critical adjustments. By mounting the variable condensers or inductances as stated above and by means of Vernier compensating.

capacities or inductances across each tuned clrcult operated. by cams, it is possible to so cut the cams as to 'maintain the three circuits in resonance over a continuous range of frequencies with but one control.

The features of my invention which I believe to be new are pointed out with particula'rity in the appended claims.

understood by the following description taken in connection'with Figs. 1, 2, 3, 4, 5, 6'

and 7. It will be understood that the principles of my invention may be embodied in various. forms and that details arenot material.

Fig. 1 shows an application in which the electrical constants of two circuits 'may be. made to be variable with respect to each other-in a definite manner'over a continuous The inven- "tion itself, however, together with further objects and advantages thereof will be best range of frequencies Withbut one control.

It is understood that this-idea is not restrictedto two circuits but to any number. By way of example, I will take the two variable circuits of the Armstrong superheterodyne receiver. Reference characters 3 and 4 are two variable air condensers -mounted on the same shaft or one to one gear connected andwith movable plates in the same relative angular position. The

- movable plates of 3 and 4 are preferably cut to a shape to give a straight line frequency relation. and so proportioned with respect --to their associated circuits as to maintain the approximate desired frequency relations. Reference character 1 is a coil antenna or coupling inductance to an aperiodic antenna which with condenser 3 constitutes the circuit tuned to thelincoming frequency. Numeral 9 indicates the inductance'of the heterodyne oscillator circuit, which with condenser 4 produces the local oscillations whose fre quency it is necessary to adjust so that when this frequency is combined with the incom- I I therefore provide a compensating condenser or inductance which is operated by means of a cam-5 which engages an arm 6 held against the cam by spring 10. The

cam rotates with the shaft carrying the two tuning condensers. The proper shape of the cam is determined as follows: Dial 2 is set at zero or so that condensers 3 and 4 are set at minimum capacity, and a frequency of that to which circuit 1-3 is then adjusted is impressed on that circuit. Compensating condenser 7' is then varied by means of adjustment screw 8 until the frequency of oscillator circuit 49-7 is suchthat when combined with the frequency being. im-

pressed on circuit 1'3, the desired beat or.

5 lntermdiate frequency is obtained. The positionof arm 6 on disc 5 (5 is at first a semicircular disc) is then marked by a dot on the 3"v .7 disc. Dial '2 is then rotated, say twoor three v "degrees, and a frequency of that to which circuit 1-'3 is then ad usted is impressed. on'that circuit and the rocess repeated. In

this way a series of ots are obtainedon disc 5, for the various positions of arm 6.

Thegilsc is then cut on the dotted line giving the cam 5 as shown by thedotted line. Then,

.for any setting of dial 2 after cam 5 has been out, the roper frequency relations of the two circuits 'must always be maintained. It isof course --understood.'that adjustment 8 is *necessary only while determining the shape of cam .5 is not used thereafter.

basis.

Another application-is shown in Fig. 2-

riable condensers are shown at 12, 13 and- 14. .The movable plates of these condensers are attached to the same shaft or arranged to be driven by one to one gears and may be rotated by one dial30. Rotating with this shaft are the'three cams, 15, 16 and 17. Each cam controls a small variable compensating condenser, 21, 22, and'23. These condensers are connected in parallel with the main condensers which are connected t the tuning inductors. The principle of o erating of the device is as follows:

The three condensers 1, 2 and 3 are as nearly equal in capacity at any setting as it is" practical to obtain them on a production The movable plates are connected to the shaft in approximately the same angular position. It will be seen that an exact adjustment of the condensers to give the same resonant frequency to each of the three tuned circuits 1227, 13'-28 and 14-29 over a continuous range of frequencies as the dial 3() is turned thru 180 degrees cannot be obtained due to inequalities of the capacity variation of the three condensers '12,

13 and 14, and to inequalities in the induct- 1 ances 10, 11 and 12. To attain this end that is, the maintenance of the three tuned circuits in exact resonance as the dial 30 is rotated, the three compensating condensers 27, 28 and 29 are adjusted by means'of adjustments 24, 25 and 26. This adjustment of the set over its frequency range is as follows: Dial 30 is set at zero andknobs 24, 25 and 26 adjusted until the three circuits are brought into resonance by the variations in the compensating capacities 21, 22 and 23. The positions of the arms, 18, 19 and 20 against the discs 15, 16 and 1'? is then marked by a dot on the disc as described above. The dial 30 is then rotated, say two or three degrees, and the three circuits again brought into resonance by adjusting knobs 24, 25 and 26 and the second location of the arms 18, 19 and 20 marked on the discru This process is continued until a series of dots have been made on the discs, as shown in Fig. 1. The discs are then out along the dotted line and the end of the arms adjusted to run on the periphery of the cam thus formed. When the dial 30 is then turned thru degrees the three circuits 12-27,

1328 and 14-29 will be maintained continuously in resonance by the variations of condensers 21, 22 and 23 which are made .to'

Vary in the-exact proportions necessary to compensate for inequalities in the constants of the three circuits.v Thus with this adjustment once made it becomes possible to operate such a receiving set by means of but N 06116 control. As in the former case adjust-' ments of 2425 and 26 are eede dbnly' w-hile determining the shapes of the'cams and are not; made thereafterfi There are of course several modifications of the arrangements-shown in Figs. 1 and '2. Some of these are. shown in Figs. 3, 4,

6 and 7. Fig. shows a combination in which-a variable condenser'31'and variomc,'- ter 33 arearranged to be variable thru their vrange by means of one manual control 78.

j compensating variometer 38-connected in circuit with condenser 31 isoperatedby-cam- 32 and a compensating condenser 35. conerated by cam 34.

nected iii-circuit with variometer 33 is ap- .Fig. 4 shows a combination in variable condenser and variom'eter42 are .arrangedto be'variable th'ru their range by meansof one manual control 79. A co1npensating condenser 47 connected in circu t with the'condenser 40 is operated by cam 41 and acom'pensating variometer 45 connected in circuit with variometer 42 is operated by cam43.

ated by cam 50, and a com nsating-variom- 'Fi 5"shows a combination in whic'hn waria le condenser 49 'and another-variable 4 condenser 51 are arranged to be variable thru their range bymeansof one manual contrbl 80. A compensating variometer- 57 connected in circuit with condenser 49 is opereter 54 connected incircuit with condenser 51 is?operated by cam 52.; 4 v 4 Fig. 6 shows an arrangement inwhlch a -'variometer 59 and another variometer 61 are "arrangedto be variable thru their range by 7 one manual} 'cont1"ol 81. A compensating cam 62.

variometer .67 connected in circuit with va ri'o'meter' 59 isfope'rated bycam and a compensating variometer 64 connected in circuit with variometer .61{ is operated by .Fig. 7 shows a combination in which a .variometer 69 and another variometer 72 are arranged to be variable thru their range bymeans of one: manual control 82. In this casethe two variable circuits are gear connected by means of one to one gears.

A. compensating condenser connected in circuit with variomet'er 69 is operated by cam and a com ensating condenser 74 con- "the two variable circuits together liy 1 I nectedjn circultwith variometer 7 2 is operated bycam 73. The methodof connecting gear 71 Fig. 7 is of course applicable to 'gs. 1,

It is not intended to limit the application of this method of unicontrol to two types of receivers, as 'itma be a'pplied to many forms of clrcuits inwhich it may be necessary to j vary-the electrical constants of two or more;

I circuits in any desired'relation with respect I to each other range."

over any desired frequency control, said condensers having connected with continuously variable condensers, each of said condensers being so connected mechanically as to be both varied by one manual in parallel with them continuously variable compensating condensers whose capacities are caused to varydependent upon the shape of the respective cam towhich they are connected.

3. In an apparatus for reception ofvradio signals the combination of means of tuning a circuit consisting of inductance and con-' tinuousl variable capacity 'tganry radio frequency ymeans of one manual controhl means forcausing by the same manual control thefrequency of a radio frequency generating circuit consisting ofqinductances and continuously variable condensers in parallel to vary in a definite relation to the frequency to which the first'named circnit is tuned.

4. In anapparatus for the receptionof radio. signals the combination of a variable condenser, a second variable condenser so connected mechanically to the first that both condensers may be variable thru a. continwous range of capacities bymeans of one manual control; a'cam operated by the same control, said cam operating a compensating condenser electrically connected in parallel with the second variable condenser, said pensatingcondenser in such a way as to maintain a desired relation between the electrical'constants of the radio frequency ci1- cuit associated with the first condenser and those associated with the second condenser.

.cam being so shaped as to operate the com- 5. In apparatus for thereception of radio signals the combination of two or more vav riable tuning condensers so connected} me'-' 'chanically to each other as to be continuously variable thruftheir range of capacities by] I means of one manual control; a cam associated and rotatable'with each condenser by the same control inductances connected across each condenser, a compensating condenser connected 1n parallel with each variable tuning condenser, 'sald compensatlng condensers being operated each by one of the said cams insuch a way as to maintain each of the circuits consisting of inductance and capacity continuously in resonance with each of the circuits consistingofthe inductance and capacity over a range of radio frequencics, said condition being accomplished with but one manual control i 6. A control system for electrical apparatus comprising a plurality of independent electrical circuits Whosev constants are con-'.

tinuously variable each having-inherently difi'erent electrical characteristics 'a single control arranged to simultaneously. adjust each of said= circuits to a given frequency,-

cams operated by said single'control, said cams 7 operating suitable continuously Vari-,

able -impedances whereby each of said cir+ c'uits is adjusted to the same frequency.

'. In testimony whereof, I affix my signature.

FRANoIs w. DUNMORE. 

